The generation of bubbles for memory and logic systems has for many years occupied considerable effort to develop the optimum design for high frequency, reliable operation -- see the publication "A New Approach to Memory and Logic -- Cylindrical Domain Devices," A. H. Bobeck, et al, Proceedings of the Fall Joint Computer Conference, 1969, pp. 489-498. A most recent publication -- see publication "Progress in All-Permalloy Bubble Control Functions," T. J. Nelson, AIP Conference Proceedings, No. 18, Part 1, Magnetism and Magnetic Materials -- 1973 (19th Annual Conference -- Boston), pp. 95-99, with particular reference to FIGS. 3, 4 -- has proposed a design of an all-Permalloy nucleator, feed ring and replicator that merge bubbles into a major loop. This Nelson design requires operation of a Permalloy nucleator of conventional size, i.e., 6-7 microns (.mu.m), bubbles such that the frequency and current limitations and bias margins thereof are much lower than desired. The present invention is considered to be an improvement invention over this Nelson design.